Recently, hybrid vehicles using engines and motors together as power sources and electric vehicles using only the motors as the power sources without having the engines are developed and manufactured, from the viewpoint of environmental protection and energy saving. Secondary batteries that can charge/discharge electricity repetitively are used as power supplies (energy sources) of the hybrid vehicles and the electric vehicles and become essential components. Above all, a lithium ion battery is a secondary battery of a high energy density in which an operation voltage is high and a high output is easily obtained. For this reason, recently, the lithium ion battery becomes important increasingly as the power supply of the hybrid vehicle or the electric vehicle.
Conventionally, technology for using an active material of a large capacity to realize the high output and the high energy density in the lithium ion battery is known. However, an active material such as silicon and SiO known generally as the active material of the large capacity is greatly expanded/contracted at the time of charge/discharge. For this reason, if the charge/discharge is repeated in a battery using the active material, degradation is likely to occur due to collapse and isolation of the active material and a cycle characteristic is bad.
As technology for resolving the above problem, technology for suppressing degradation of the active material by using a binder having high coatability for an electrode material and high adhesion is disclosed in PTL 1.